1. Field of the Invention
This invention relates to a method of producing flexible joints and to a flexible drywall joint compound, and more particularly to a method of producing flexible joints in fabricated housing drywall construction and to a drywall joint compound that does not harden upon curing.
2. Background of the Invention
Manufactured housing continues in its popularity of producing good quality homes for relatively lower cost compared to custom built homes. Entire home surfaces, such as floors, ceilings or walls, having dimensions in excess of 20 by 80 feet are constructed in this manner. Such surfaces must be blemish free when installed and still maintain a level of fire resistance and structural integrity.
Typically, the construction of drywall surfaces is a multi-step process of finishing the joints formed by abutting edges of drywall panels. First, a prefill coat of a joint compound is contacted with the joint. This prefill must be allowed to dry (approximately 1 to 8 hours) before proceeding to the second step. The second step is the application of an embedding coating into which is pressed joint tape before said embedding coat dries. After the embedding coat dries, which can take up to approximately 1 to 3 hours, the third step follows, involving applying a "feathering" coat to the now taped joint. That coat must also dry for the same amount of time required for the first two coats. Finally, the fourth and final step involves applying a finishing coat to cover all preceding coats. The finishing coat also has a drying time requirement. All total, the fabrication process can require up to 24 hours, primarily due to the drying time requirements involved.
A problem exists in current wall and ceiling manufacturing processes whereby differences in the textures of the drywall face paper and the joint compound result in unequal absorption characteristics viz-a-viz subsequent coating applications. Also, the problem of "joint banding" or "photographing" occurs when raised paper fibers develop as a result of the inadvertent roughening of the drywall paper during sanding operations. These surface abnormalities prove difficult to hide, particularly when followed by the application of gloss or semi-gloss paints.
Methods exist to conceal these abnormalities, including applying a skim coat of the joint compound over the entire wall surface in an effort to provide a painting surface with uniform porosity and texture. However, skim coats do not have sufficient "hold out" to prevent the penetration of water or solvent from the finish coat of paint. To address this problem, primers and sealers must be used. Sealers must have a resin content high enough to lay down a film for good hold out. Primers must be added to build up the film so that texture differences are concealed. An alternative approach, as disclosed in U.S. Pat. No. 4,820,754, supplants the need of primers and sealers by a special paint formulation.
All of the drywall surface fabrication and finishing steps and alternative methods discussed supra require large amounts of time to complete. A major bottleneck, then, in each step of the fabrication process is the necessity to allow applied coatings and films to completely dry before subsequent treatment. One finishing system (U.S. Pat. No. 5,079,042) claims to eliminate the need for taping via the incorporation of fibers in the joint compound mixture. However, that process still requires that the applied coatings thoroughly dry prior to further treatment.
The problem of idle operations in drywall fabrication is no where more acute than in the manufactured housing process, whereby from 7 to 18 floors must be fabricated and transported per plant per day.
Problems also occur when manufactured homes or manufactured home modules are moved from the point of fabrication to the home site. Invariably, the action of transport results in excessive mechanical stress which causes cracks to form in the joints of fabricated drywall surfaces. Repair to these joints can cost hundreds of dollars, while providing less than optimal results cosmetically and structurally. Ultimately, this added cost is borne by the home owner.
To date, nothing exists on the market to expedite fabrication of drywall surfaces, or to provide a low cost alternative to after-fabrication repair of drywall surfaces, and large surfaces containing joints.
A need exists in the art to provide a joint compound that can be coated or otherwise manipulated while still wet. Upon curing or setting, the compound also must maintain a level of flexibility to prevent manufactured housing modules from cracking at drywall joints during transport or final assembly. The needed joint compound and method for construction must be cost effective compared to costs associated with after-fabrication repair, said repair occurring either at the end of the fabrication process at the factory, or at the homesite.